Process of improving aluminum alloys



Patented Ma 24, 1927.

MANY.

WILLIAM GUERTLER, OF CHARLOTTENBURG, AND WILHELM SANDER, 0] E88,

GERMANY, ASSIGNOBS TO THE FIRM:

TH. 'GOLDSCHMIDT A.-G., OI ESSEN, GER- IPBOCESS OI IMPROVING ALUMINUM ALLOYS.

Io Drawing. Application filed Kay 6, 1926, Sort This invention relates to a process of improving aluminum aluminum zinc-magneslum The properties of this alloys, alloys.

particularly alloy are greatly improved if the zinc and magnesium are compound of about inc. This aluminum and behaves towards it as a new element with its characteristic properties.

Although aluminun1-zinc-magnesium loys are well-known, the zinc nesium components in such proportions as to combine to form the compound MgZn even W these alloys were subjected to a ment or ageing process.

aland maghave not been alloyed completely hen heat treat- Exhaustive experiments have shown that the improvement in tensile strength, etc., for

ure aluminurn-MgZn withthe resence of about 4% MgZn stituent of the alloy is than 26% by weight because the amount of hard and brittle MgZn decreases the workability loy and alloy counteracts the improving action.

alloys commences by weight of n practice the amount of this connot increased to more increasing crystalline of the althe increasing brittleness of the The best results with respect to workability and strength are obtained if the amount of the compound MgZn lies between 4% and 12% by wei ht.

Additions of other substances forming a solid solution with aluminum such as for example beryllium, silicon,

copper vand the like not only do not interfere with the improvin process but on a furt er improvement. rally be taken to adjust MgZn corres ondingly such other su stances because of these components the MgZn compound in alumin the contrary efi'ect Care must natuthe amounts of the on the addition of the addition alters the solubility of um in the solid state. If components are added which have a zinc, sue

eater atn'nity for magnesium or ,as silicon, which forms a comound Mg Si which is more stable than Zn then the amount of the zinc must be re ueed correspondingly in accordance with the added amount of such component, so

an 110. 107,213, and in Germany November 22, was.

that the remaining free magnesium can be completely-transformed wit the zinc into the compound MgZn The strength of the aluminum alloy containing MgZn as the main com onent, may be considerably increased by adding small amounts of high-melting components such as manganese, nickel, titanium, tungsten, molybdenum and the like. The amount of these additions must not exceed about 1% because the workability of the alloy will otherwise be adversely affected.

A further improvement may be obtained if the ageing of the alloy after annealing and quenching is carried out at high tem eratures. This applies particularly to al oys containing a high proportion of Mgzn The agein at high temperatures can be efiected imme iately after quenching, after an intermediate ageing at room temperature or also after a completely finishing ageing at room temperature. This enables alloys of various different strengths and elongation properties to be obtained as desired.

High strength values can be obtained if after being aged at room temperature (about 5 to 8 days) the alloys are submitted to a further after-ageing at higher temperatures. It is also possible bysuitably selecting the ageing temperature to obtain a material of different strengths and elongations. It is of course necessary for every case, to ascertain the most favourable temperature and duration of the ageing corresponding to the composition of the alloys by practical tests. In general, these temperatures lie between 50 to 150 0., whilst the duration of ageing is from 3 to 48 hours. A

In order to obtain the high strength values the following method is preferably used:

The mechanically worked alloy is annealed for some time. at temperatures going up to about 550 C. The best annealing temperatures lie between 450 and 520 C. The time for annealing the product depends on the size of the latter and generally varies from 15 to 60 minutes. After annealing the material is removed from the annealing furnace and subjected to a quick cooling, for instance by quenching in water having a temperature of from 15 to 20 C. A slower cooling is advantageous if a higher elongation but less strength is desired. For this purpose the material is preferably quenched in oil at a temperature of 20 to 100 C. After such treatment the material is either subjected to a self-ageing measure by storing it for five days at room-temperature (about 15 to 25 0.), whereby the strength increases while the elongation remains the same or decreases but little, or the annealedTmd quenched material is subjected for a shorter period (3 to 48 hours) to ageing athigher temperature (about: 50 to 150 (1.). When working in such a manner especially high values of strength are obtained, the elongation values however, being lower.

Ewample I.

An alloy containing 9% MgZn shows after ageing at room-temperature (about 15 to 25) strength valves of about 44 kg/mm and elongation values of 18 to 22%.

Emma-pie [1.

The same alloy sllOWs after an ageing of 15 hours at a strength of 46 to 48 kg/mm and elongations of 17 to 19%.

A further improvement will be obtained if small amounts of components having high melting points are added to the aluminum Mgzn -alloys. By this means not only the strength but also the resistance to corrosion is increased. These alloys are not affected by overheating. Even if they are considerably overheated as may be the case by an interannealing during the rolling-process, they do not show any tendency for recrystallization, which would result in formation of a coarse grain and would be very detrimental to the strength qualities.

Example [11.

An alloy containing 9% MgZn and 1% manganese, nickel, titanium or other metals of a high melting point, rolled into sheets having a thickness of 1.5 mm. shows after annealing, quenching and tempering at 60 (J. during 15 hours a strength of .17 to 52 kg/mm and elongations of 15 to 18%. The same values were obtained when the sheet was intentionally overheated by an intermediary annealing during the rolling process.

Further experiments have shown that more improvement of the alloys can be obtained if other components are added, such as the compound Mg Si for instance, forming a solid solution with the aluminum.

Example IV.

An alloy containing 9% MgZn 1% manganese. 0.5% Mg Si shows after the prescribed process of improvement strength values of 52 to 57 kg/mm and elongations of 12 to 15 9 0. I

Aluminum alloys possessing such high strength values have not heretofore been roduced. The strength values of these al oys may be further increased by using higher tempering temperatures. for instance 110 C. However, the elongation will decrease in such a case. Generally a tempering temperature of 60 to C. and a tempering time of u to 15 hours will be sufiicient.

\ hat we claim is:- 1

1. A process for producing alloys of high tensile strength comprising alloying aluminum with MgZn. said compound forming from 4% to 26% by weight of the alloy, and subjecting the alloy to annealing, quenching, and ageing.

2. A process for producing alloys of high tensile strength comprising alloying aluminum with MgZn said compound forming from 4% to 26% by weight of the alloy, and subjecting the alloy to annealing, quenching, and ageing at temperatures ranging from 50 to 150 C.

3. A process for producing alloys of high tensile strength comprising alloying aluminum with MgZn. said compound forming from L76 to 26% by weight of the alloy, adding minor quantities of elements forming solid solutions with tllllll'lllltlll], and subjecting the alloy to annealing, quenching, and ageing.

4. A process for producing alloys of high tensile strength comprising alloying aluminum with MgZn said compound forming from 4% to 26% by weight of the alloy, adding minor quantities of elements having high melting points, adding minor quantities of elements forming solid solutions with aluminum, and subjecting the alloy to annealing, quenching, and ageing.

In testimony whereof we aflix our signatures.

WILLIAM GUERTLER. WILHELM SANDER. 

